Force-, power-, and elasticity-velocity relationships in walking, running, and jumping

Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were found to vary in the following order (from highest to lowest): long jump take-off, maximal running speed, submaximal running (80, 60, and 40% of maximum speed), racing gait, and normal gait. The data disclosed that the measured parameters had the highest values in the long jump take-off performed by the long jump athletes. Their peak values were: resultant ground reaction force 3270 +/- 74 N and mechanical power 160.1 +/- 10.5 J x kg-1 x s-1. For the track and field athletes the values were 2010 +/- 80 N and 126.0 +/0 12.6 J x kg-1 x s-1. The apparent spring constant values of the support leg in the national level jumper group were in eccentric phase 30.54 +/- 8.38 N x mm-1 x kg-1 and in concentric phase 0.129 +/- 0.012 N x mm-1 x kg-1. In the track and field athletes the values were 13.97 +/- 1.01 N x mm-1 x kg-1 and 0.093 +/- 0.003 N x mm-1 x kg-1, respectively. In general, the increase in force and mechanical power output was related to the value of the apparent spring constant of the support leg in the eccentric phase. The spring constant in the eccentric phase increased with the velocity of motion in running, the long jump take-off and the triple jump. This suggests that it may be possible to use this parameter as a measure of mechanical performance, as it may reflect the combined elasticity of muscles, tendons, and bones.